mir-borrowck: print values in error messages in the same way that the AST borrowck
mir-borrowck: print values in error messages in the same way that the AST borrowck

- Print fields with `.name` rather than `.<num>`
- Autoderef values if followed by a field or an index

graydon/rust,aidancully/rust,graydon/rust,graydon/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust,graydon/rust,graydon/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,aidancully/rust,aidancully/rust